Microsurgery, in which a medical surgical microscope is used to observe affected parts while performing surgery, has been studied and introduced in the surgical operation field.
In such microsurgery, a stand is needed to install weighty objects, i.e., a surgical microscope with its attached devices; place them in a desired space; then maintain their position.
Generally, in the balance structure of such a stand, the middle part of a link unit using a parallel link is rotatably connected to a holding unit, while a surgical microscope is installed at one end of the link unit and a counterweight is placed at the other end of the link unit, centered on the point of rotation, in order to offset the weight of the surgical microscope.
Since a surgical microscope is mounted with attachments such as an assistant scope or a video camera, etc., the position of a counterweight is adjusted based on the total weight of the surgical microscope to maintain the overall balance between the surgical microscope and the counterweight.
However, in case when a surgical microscope and its attached devices remain in the desired position, their vertical balance needs to be maintained, but a conventional stand has difficulties to control the vertical balance due to the inconsistent total weight of a surgical microscope by the presence of various attachments.